NASA scientist says this is where we'll likely find alien life first

Take a good look at all of the planets and the most-prominent
moons in our solar system and ask yourself which one is most
ideal for life. Would Earth be your first pick?

Radu Stoicescu

If you know what to look for, the lush green continents and deep
blue oceans adorning our planet's surface would be a dead give
away that water, and life, are already here.

Unfortunately, for astrobiologists like Chris
McKay, Earth is the only place that's blooming with signs of
life visible from space. If aliens are hanging out somewhere
nearby in our cosmic neighborhood, they're going to be much
harder to find than a quick fly by.

Where to begin

"Things are better below the surface," McKay, who's a senior
scientist with
NASA's Planetary Systems Branch and investigates where else
life could exist in our solar system, told Business Insider. "And
so where we really want to go is below the surface."

The big problem with this is that designing and dispatching a
lander that can dig deep beneath the surface of a planet to
search for signs of life is incredibly difficult, not to mention,
expensive. So far, the only places we've drilled, collected, and
examined samples beneath the surface is the Moon and Mars.

The one exception where we wouldn't need to dig and drill is on
Saturn's tiny moon Enceladus, which harbors a massive ocean
underneath a thick layer of ice on its surface.

Enceladus was recently in the news for the compelling evidence
two different teams of scientists found indicating
active volcanoes lining the seafloor, but that's not why
McKay is so excited about this tiny moon.

"Enceladus is most likely to give us an answer soonest,"
he said. "The reason is Enceladus has a plume coming into
space."

In 2005, the Cassini spacecraft flew by Enceladus and spotted
plumes of water vapor and other materials gushing out its
surface. If there's life in the solar system, the first place
we're likely to find it is inside of those plumes, McKay said.

What to look for

Sadly, Cassini is not equipped with the right instruments to
detect signatures of life in these plumes. And right now, NASA
has no plans to dispatch another probe to Saturn or its moons
anytime soon. But, that's not stopping McKay and others from
discussing what they'd look for if they had the chance.

"I'd suggest that the best molecules to measure are amino acids,
the building blocks of proteins," McKay said during a
live webcast hosted by The Kavli Foundation in January.
"...life on Earth has made specific choices in amino acids. It
uses a set of just 20 amino acids to build proteins, and those
amino acids are all left-handed."

Left-handed amino acids are chemically identical (meaning they
have all the same atoms in the same amounts) to right-handed
animo acids. The difference is that they are structured in a way
so they're mirror images of one another, just like how your right
and left hands are the same shape but don't line up when you put
one on top of the other.

One of the
outstanding mysteries in astrobiology is why RNA and DNA is
only constructed from proteins built by left-handed amino acids.
Regardless of why or how, this fact will come in handy during
potentially future studies of Enceladus.

"If Chris were to find amino acids in the plume of Enceladus, the
challenge becomes determining whether they are the products of a
biological process," Steven Benner, who is the president and
distinguished fellow at the Foundation for Applied Molecular
Evolution in Florida, said during
the webcast. "If he were to find that they're all the same
hand, that would be convincing, because that's what makes the
protein evolvable."

The real question

For McKay, the excitement of the hunt is not just about
discovering whether aliens exist. It's discovering unique alien
life that is completely different from life on Earth, which might
be quite a bit harder since the building blocks of life are so
complex.

"To my mind that's the real question: Not 'is there life on these
other worlds' but 'is there a second genesis of life on these
other worlds'," McKay told Business Insider. "That's a subtlety
that's not obvious until you think about it."

A second-genesis of alien life could, in theory, have a
completely different biomolecular structure from life we see on
Earth. Right now, scientists debate over whether or not life on
Earth originated on another celestial object, like Mars, that
then hitched a ride to Earth inside of a meteorite.

That is not a stretch to imagine, researchers say, since
Mars was covered with liquid water around the same time that
life is believed to have begun on Earth. If we do find evidence
of life on Mars and it has the same DNA as us, then it's probably
our cousins, McKay told Business Insider.

If we want to find truly unique alien life, then we'll have to
travel farther than next door.

"As we go from Mars to Europa to Enceladus to Titan, as the
worlds get farther away from Earth the conditions get less and
less like Earth," McKay said. "We're more likely to find life
that's not related to us the farther out we go."